Apple's Shares Drop as Slowing Growth Builds on Investor Worries

Apple Inc. shares fell as much as 12% Thursday as slowing revenue and profit growth further fanned investor concerns about the company's momentum and consumer demand for its devices.

In its highly anticipated December quarter report, Apple reported its slowest sales growth in more than three years, despite introducing a new smartphone and a smaller tablet. Meanwhile, Apple's flat earnings reflected the higher costs the Cupertino,...